In situ integration of CoFe alloy nanoparticles with nitrogen-doped carbon nanotubes as advanced bifunctional cathode catalysts for Zn-air batteries.

Electrochemical catalysis of O2-incorporated reactions is a promising strategy for metal-air batteries. The performance of metal-air batteries is determined by the catalytic activities of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Therefore, developing efficient catalysts with superior activities for the ORR and OER is of great significance to expand the application range of metal-air batteries. Herein, CoFe alloy nanoparticles adhered to the inside wall of nitrogen doped carbon nanotubes (CoFe@NCNTs) are synthesized and can function as a Janus particle to efficiently catalyze the ORR and OER with desirable activities in 0.1 M KOH solution. Specifically, the CoFe@NCNTs present an onset potential of 0.95 V and a half-wave potential of 0.84 V as an ORR catalyst. When used as an air-cathode catalyst for a Zn-air battery, the CoFe@NCNTs cathode performs better than a Pt/C cathode, showing a high open-circuit potential of 1.45 V, a maximum power density of 150 mW cm-2 and an average specific capacity of 808 mA h gzn-1 at current densities from 2 mA cm-2 to 10 mA cm-2.